The use of suction cleaning for carding machines has become increasingly important as the speed of production has increased during the past several years. Heretofore, the suction cleaning of carding machines has been generally confined to the area of the lickerin, the area of the doffer roll, and under card cleaning. See for example, U.S. Pat. No. 3,315,320 to Bass et al., U.S. Pat. No. 3,304,582 to O'Neal et al. and U.S. Pat. No. 3,150,415 to Reiterer. See also patent application Ser. No. 587,277 filed Oct. 17, 1966 by John E. Crowley, Jr. entitled DOFFER PLENUM, now abandoned.
The doffer plenum described in the Crowley application is in general use today for the suction cleaning of the doffer end of a carding machine and comprises a plenum of generally arcuate cross-sectional configuration adapted to be positioned directly above and on the doffer cover of a carding machine. The Crowley plenum is connected to a central source of suction and includes a suction inlet facing the nip between the main cylinder and the doffer cylinder and a second oppositely directed suction inlet facing the take off roll and crush rolls. A web cover of planar configuration is hinged to the front edge of the Crowley doffer plenum and extends over the take off roll and toward the crush rolls to protect the doffer cylinder and newly formed web after it leaves the doffer cylinder from contamination by airborne lint and debris.
Despite the protection afforded by the web cover illustrated and described in the Crowley application, the newly formed web as it passes from the take off roll through the crush rolls to the trumpet to be formed into silver is subjected to contamination from the scrapings of the scraper blade conventionally mounted to clean the top crush roll of impurities picked up from the web passing therebeneath.
Prior efforts to automatically remove the accumulations of debris and foreign matter released from the crush roll by the scraper blade include that shown in U.S. Pat. No. 3,355,774 issued Dec. 5, 1967 to Yukimasa Miyagi. Miyagi discloses the direct application of suction to the top and bottom crush rolls at the points where they are engaged by scraper blades. The suction inlets provided by Miyagi are closely spaced to their respective scraper blades and appear to be connected to a source of suction independent of any other suction cleaning apparatus on the carding machine.
U.S. Pat. No. 3,340,577 issued Sep. 12, 1967 to Morrow et al. contains a disclosure of a clearer roll frictionally engageable with and driven by the top crush roll. The clearer roll includes a flap which periodically compresses the debris accumulated on the clearer roll and discards it from the clearer roll. A suction tube is spaced from the clearer roll and its associated crush roll and it is intended that the debris disloged from the clearer roll will be picked up in the suction tube. Actual experience has established that only a portion of the dislodged material finds its way to the remotely spaced suction tube of Morrow.
The Crowley doffer plenum disclosed in said abandoned application Ser. No. 587,277 included suction inlets in the form of the doffer plenum facing the crush rolls and the web cover extending over the take off roll and toward the crush rolls was intended to induce a sufficient negative pressure about the crush rolls to carry away accumulations of lint and foreign matter dislodged at the crush rolls.
Each of the aforesaid efforts to remove the foreign matter released at the crush roll has proven ineffective to reliably and consistently keep the accumulations of foreign matter from falling into the web of processed fibers as it passes from the crush rolls to the trumpet to be formed into sliver. The contamination of the web with the foreign matter removed at the crush roll results in a poor quality of sliver and a consequently poor quality of yarn.